The short answer is not much, basically whatever you can get for it. That was never a quality instrument like Martin or Taylor. It was a budget instrument when it was new. It depends on its tone and playability, neither of which you mentioned. If it plays and sounds acceptably then I'd guess it would bring $150 or so.

By they way, there's a difference between old and vintage. A pre-war Martin is vintage while an old cheap guitar is just plain old.